Protective device for distribution systems.



R. M. OSTBRMANN.

PROTECTIVE DEVICE FOR DISTRIBUTION SYSTEMS.

APPLICATION FILED 110 7.2, 1908.

1 ,OQO,934;, Patented Aug. 15, 1911.

4 SHBETS-SHEET 1.

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. Rudolf M05 ermann. 4. My; 1 y.

RJM. OSTERMANN.

PROTECTIVE DEVICE FOR DISTRIBUTION SYSTEMS.

APPLICATION FILED NOV. 2, 1908.

I Patented Aug. 15, 1911.

4 SHEETS-$111131 2.

Wimesses: lr'wenfior 5M Rudol M.Osermanh.

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R. M. OSTERMANN.

PROTECTIVE DEVICE FOR DISTRIBUTION SYSTEMS.

APPLICATION FILED NOV. 2, 1908.

Patented Aug. 15, 1911.

4 SHEETS SHEET 3.

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R. M. OSTBBMANN.

PROTECTIVE DEVICE FOR DISTRIBUTION SYSTEMS,

APPLICATION FILED NOV. 2, 1908.

1,000,934, Patented Aug. 15, 1911.

4 SHEETS-SHEET 4.

Fig.5.-

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Rudol MOseermcmn. V

UNITED STATES PATENT OFFICE.

BUIDOLF I. OS'I'EBMANN, OF BOGOTA, COLOMBIA, ASSIGNOR TO GENERAL ELECTRIC COIPANY, A CORPORATION OE NEW YORK.

r'no rrcrlvia: DEVICE ron DISTRIBUTION SYSTEMS.

Specification oflett ers Patent. P t t d Aug 15, 1911, Application filed November 2, 1908. Serial No. 460,795.

To all whom it may concern.

Be it known that I, RUDoLr M. QsTnR- MANN, a subject of the King of Prussla, residin' at Bogota, United States of Colombia, gout-h America, have invented certain new and useful Improvements in Protect ve Devices for Distribution Systems, of which the following is a specification.

My inventlon relates to protective devices for systems of electrical distribution and more particularly to systems in which parallel transmission lines are connected to the same bus bars of the substation or other distributing point.

It is customary in systems distributinglarge amounts of energy touse two or more parallel transmission lines between the gencrating station and the important substations in order to prevent interruption of the service by damage to one of the transmission lines. If a transmission line is'damaged, it is disconnected from the system by automatic switches or circuit breakers, usually installed at each end of each transmission line and controlled by protective devices,'commonly called reverse current relays, which are responsive to reversed energyfiow and open the switches to prevent the damaged line drawing current from the system. 'Y It has been found in practice that the reverse current relays commonly used operate not onlyon reverse energy flow but also on excessive flow'. of current in the normal direction. A Short circuit on one of the transmission lines will reverse the direction of energy flow in that line and will cause the reverse current relaycontrolling that line t' operate, but it is apt to cause in the other transmission lines a heavy rush of current whlch, although 1n the normal direction,

will nevertheless operate the reverse current relays corresponding to the other lines, hence all the switches are opened and the service to the substation interrupted.

The object of my invention is to provide parallel transmission 'lines with protective devices which will in response to reverse energy flow due to damagefto a transmission line Select and cut out the damaged line and also prevent the healthy transmission lines being cut out by a'heavy rush of current in the normal direction; to increase the sensitiveness and accuracy of the reverse current relays; ,and to interlock the proteclected and cut out while one of the transmission lines,

tive devices and the automatic se'ctionalizing switches of the bus, thereby preventing a heavy rush of current through thebus opening' the sectionalizing switches while the protective devices are in operation.

In carrying out my invention protective devices responsive to reverse energy flow are connected to 'each transmission line and are interlocked in such a manner that the damaged transmission line is automatically seat the same time the protective device becomes unable to cut out the healthy transmission line. This result is preferably accomplished by connecting reverse current relays to the same phases in each transmission line and interlocking the relays of each phase by means of an .interlock arranged to permit that relay correspending to the damaged transmission line to move into 0 erative position and at the same time rendiir the otherrelays inoperative. and unable to respond to those heavy currents in a normal direction which have heretofore caused trouble by operating the relays;

The operating forces are small in reverse current relays as commonly constructed with opposed current and potential coils, since the potential coil is always energized and must not be strong enough to lift the core unaided,and, therefore, in accordance with my invention, the operating forces and the sensltiveness of the reverse current relays are both increased by means of an intensifying device or auxiliary relay which is in operation only during reverse energy flow on and when operated connects the reverse current relays into circuit, thereby permitting the use of large currents in both coils of the reverse current relays, sincethe currents flow through the relays only for the short period of time required to bring the relays into act-ion and to open the switches.

Where the busbars in the substation are sectionalized, it is desirable to prevent the sectionalizing switches being opened by the rush of current in the bus caused by a short.

circuit on a transmissiolf line and my invention therefore contemplates means for automatically preventing. the opening of the bus sectionalizing switches during reverse energy flow, and the preferred arrangement for Securing this result is some .form of device for rendering the sectionalizing switches non-automatic during the time the reverse current relays are in action,

a .this device preferably being controlled by means of the auxiliaryrelay which brings the reverse current relays into action.

My invention will best be understood in.

connection with the accompanying drawings, which are merely illustrative of one of the many forms in which it may be embodied and in which Figure. 1 is a diagram showing a substation with two transmission lines controlled lay; and F ig. 6 isa plan viewof the same showing the arrangements of contacts.

:Irrgthe arrangement shown in Fig. 1, the

transmission lines, bus 'bars, and feeders,

which are usually pol base, are represented by'single lines to simplify the drawrng.- ZPhe' bus bar 1 in the substation supplies the various feeders 2 and in turn is mission line side wit supplied from the two parallel transmission lines 3 and 4 through transformers 5 and 6. Each transformer may be disconnected from the transmission lines by means of auto-v matic oil switches or c1rcu1t breakers 7 and 8 and also from the bus bars by means of similar automatic switches or circuit'breakers9and10.

In the arrangement shown in Fig. 1, the transformers are rovided on the transa connecting'switch 11 to enable both transformers to be supare provided with. trip coils 12 energized from current transformers 13 and 14, preferably placed between the transformers and I the bus bars to cause the protective device to act in case of a break down in the transformers as well as on the transmission lines.

The supply 7 of current from the current transformers to the trip coils of the switches is controlled by any suitable protective dev1ce or relay responsive to reverse energy flow. In the arrangement shown in the drawing, a. reverse current relay is connected to each transmission line, these relays comprising current coils'15 and 16, connected to the two current transformers 13 and 14, and potential coils 17 and 18, energized from the potential transformers 19 connected to the bus bars. The current and potential coils of each verse current relay cooperate and exert a. combined effect upon the movable armatures or cores 20 and 21, which controlthe supply of current to the trip coils 12 by means of short circuiting' energy is supplied to that line from the bus bar, the relation of the currents in the two coils changes, and the two coils cooperate to move the armature of the reverse current relays.

It has been found in practice that the reverse current relays of the type above described often fail to discriminate between a short circuit and reverse energy flow, and

unless some provision is made to overcome this defect, the two relays shown 1n Fig. 1

are apt to trip at the same time, particularly on a short circuit on one of the transmission lines, since'each relay can only be adjusted to trip When there is sufiicient magnetizing force to set the core in motion. If the core is once started, it keeps on moving until it reaches operative position, because the force of attraction increases as the core enters the coils of the solenoid. The number of turns of the voltage coil must be made so small that with normal voltage and no current in the current coil the core is. not raised and consequently currents which are often met with as a result of damage to a transmission line will energize the current coil to such an extent that it will overpower the voltage coil and raise the core, particularly if the current in the voltage c'oil decreases on ac-- count ofa. drop in voltage, or is out of phase with the current in the current coil.

The difliculty above noted is overcome in my invention by flexibly or resiliently interlocking the cores 20 and 21 of the relays by means of a flexible cord or Wire 24, which passes through guide pulleys 25 and over a tension pulley 26 carried upon a movable;

frame 27 and controlled by a tensioning device such as a spiral spring 28,'which engages the frame 27 and is carried upon an adjustable step 29, as shown in Fig. 3: The position of the step 29 may be adjusted by means of the thread on one end of a calibrating screw 30 which is reversely threaded at opposite ends, and is carried in suitable brackets, while the calibrating stops 31,

which determine the position of the cores in relation to the coils, are controlled by'the thread at the other end of the screw, hence rotation of the screw causes the step :29 and it operates, so that the core may more through a considerable distance before. e11- gaging and operating the switch.

The interlock is so proportioned that when either of the two cores is pulled up, the

spring 28 is compressed until finally the frame 27 cannot move downward anyfarther and is held stationary by the'step or pro- :jection 29. 1 Both plungers, if attracted at the same time and with equal force, will be accelerated with the same speed and both will reach the same height, until they are stopped by the cord or Wire which interlocks them, and neither of the cores is able to reach operative position and actuate its corresponding short circuiting switch. The flexible interlock comprlsmg the core and pulleys is superior to a rigid interlock, since it allows either core to travel free and unhampered by'the counterbalancing ofthe other one, until the spring 28 is entirely compressed, and since the core with the greater magnetic pull can accelerate more quickly than the other one, it reaches operative position first and renders the other core unable to affect its short circuiting switch, since only one core can move into operative position at one time.

When both lines are in operation and a shoi'tcircuit,occurs on one of the feeders, both transmission lines will carry the same heavy current if they'are bot-h of the same condition. Even though as a result of the short circuit the voltage of the system drops so much that the current coils overpower the volta 'e coils of the reverse current relays both cores will be pulled up with equal force but neither can travel far enough to trip either of the switches on account of the interlock above described, and under ordinary conditions, short circuits on the feeders will not usually trip the transmission line and transformer switches. If a short circuit or other derangement occurs on one of'the transmission lines the current and potential coils on the relay corresponding to that line cooperates and quickly bring the core of the relay into operative position, cutting out the damaged transmission line and at the same time preventing the other core reaching trippingposition, which it tends to do 111' response to heavy current through the and leaves the core of the otherrelay in' position to respond to the heavy current through its current coil caused by a short circuit on one of the feeders, and such a short circuit might therefore shut down the system before the transformers which were cut out on account of trouble on the transmission lines have been 'put back on the.

circuit.

It is often desirable to disconnect the transmission lines during operation by very small amounts of reverse current, caused by leakage so slight that it' doesnot seriously afiect the line voltage, and in such a case the difference of magnetizing force between the current coil and the potential c'oil may not be great enough to bring the relay into action. It also happens at times that the voltage of the system drops down and the current in the potential coils lags, especially at heavy short circuits, until the influence of the potential coils is not sufiicient for Working the relay either way, since the number of turns permissible for the potential coil is limited by the fact that the cores must be unaffected at normal voltage and no current. The disadvantages above noted are obviatedin accordance with my invention by means of some auxiliary devicewhich multiplies the effect of the relay coils and energizes them only during the time'trouble is present on either transmission line and which keeps the relay coils out of clrcu t when a short ,CllfCllli'. occurs on the feeders. Such an auxiliary relay or device may assume various forms without departing from the spirit of my invention, but one form which may beu'sed is shown diagrammatically in F ig. 4 in which my invention is shown embodied in a substation supplied by two parallel threephase transmission lines, although, obviously I the number of phases makes no difference in the principle of operation.

The arrangement shown in Fig. 4 corrc- I .110

sponds with that shown in Fig. 1 with the addition of the auxiliary relay, and each transmission line is provided with two cur.- rent transformers 13 and 13* 'and' 14k and 14,

which are connected to the tripping coils.

12 of'the switches, the transformers 13 and 13 also being connected to the currentcoils 1515 respectively, while -the. tra'nsform-.

ers 14 and 14 are also connected to. the

current coils 16 and 16, respectively, of

two sets of interlocking relays such as above described and shown in Figs. 2 and 3. 2 The relays having cu'rrentcoils 15 and 16 are therefore connected to corresponding phases.

on the two transmission lines, and arein terlocked, whlle'the other two relays are also connected to corresponding phases and are interlocked. The potential'coils of the relays are supplied from potential trans formers 19-19", and since both the current and potential coils are connected into circuit only when the auxiliary device or relay is actuated and are energized for only a ely few seconds the magnetization can sa be carried to such a point that the difference of magnetic forces of the relay-coils ismore than sufiicient to give a start in the desired dlrectlon. An auxiliary device or relay 1s provided for each transmission lme,

' comprising current coils 13 and 14", enerthe auxiliary device or relay connected tocorresponding phases of the two transmission lines are oppositely wound and are provided with movable cores 34 and 35 which carry at the lower end bridging contacts 36 and 37 for closing the circuit of the potential coils of the relays. When the auxiliary relay is energized the current coil 15' of the relay and current coil 13 of the auxiliary relay are connected in series, but under normal conditions the bridging contact 38 actuated by the core 34 of the auxiliary relay short circuits the current coil 15 and thereby causes the current to flow through the bridging contact 38 instead of through the current coil 15. The connections between the other bridging'contacts of the auxiliary relay and the current coils of the relays are similar so that under normal conditions the bridging contact 39 of the auxiliary relay permits current to flow around the current'coillti, bridging contact 40 permits currentto flow around the current coil 15 of the relay andbridging contact 41 permits current to ow around current coil 16 of the relay, these current coils being throwninto series with the current coils of the auxiliary relay when the auxiliary relay is energized and the bridging contacts are lifted.

The construction of one element of the auxiliary device is shown in detail in Figs.

5 and 6, in which the current coils 13 and 14 of the left hand side of the auxiliary device shown in Fig. 4 are mounted in an iron casing and arranged to cooperate to move the core 34. The contacts 38, 39, and

50 are made in the form of segments of a the spring 54 and lifting the rod 53 and at the same time through the spring 56 lifting the rod 57, thereby bringing the bridgmg contact 36 into engagement with the fixed contacts.

Sinoe thecurrent coils of the auxiliary relay or device are oppositely wound and are connected to current transformers on corlines, the cores 34 and 35 are unaifected as long as the currents of the two transmission leak occurs on one of the transmission lines the currents are no longer in phase and the I two current coils of the corresponding auxiliary device or relay cooperate to raise the core, thereby closingithe circuit through the potential'coils and simultaneously opening the shortcircuit around the current coils of the interlocked relays, whereupon heavy currents flow throughboth the current coils and potential coils of the interlocked relays and cause one or the other of the relaysto operate quickly and definitely; As the relay cores'are lifted the corresponding short circuiting switches 22, 22, and 23, 23 are operated, opening the short circuit through the trip-coi1s 12 and permittin the full lines arein phase. If a short circuit or bad responding phases of the two transmission current from the current trans ormers to cuits the current coils 13" and 13 throughthe short circuiting switches 44 and 45. Since the opening of the switch 7, for ex-. ample, cuts off current from the coil 13 by opening the transmission line and thereby depriving the current transformer 13 of current and at the same time short circuits the coil 14 fed from the transformer 14 in the other transmission line, the core of the auxiliary relay drops as soon as the switch 7 opens and the'reverse current relay coils are cut out of circuit. I The bus sectionalizing switch 46 is prevented fromopening automatically by any suitable arrangement which is controlled by the auxiliary relay and in any suitable way renders the sectionalizing switch non-automati'c during the time the auxiliary relay is energized. Inthe specific arrangement shown, the switch 46 1s provided with a ,trip coil 47, controlled by short circuiting relays 48, each relay being provided, as shown in the figure, with opposed windings supplied with current from the current transformers 49 in the busses. Under normal conditionsone of the windings is short ci-rcuited by the short circuiting switches 50 mounted on the upper end of the cores of the auxiliary devices or relays, and the sectionalizing switch will therefore open automatically under overload, since the section of the coil which is not short circuited will operate to lift the core of the relay in case of an excessive current in the bus, but as as the auxiliary relay operates and one of the switches 50 is opened the short circuit on the other part of the relay winding device again assumes the normal pos tionw is removed, the two windings counteract each other and the sectionalizing switch is non-automatic until the auxilia y relay or shown in the drawing.

My invention may be "embodied in many other forms than that shown and described,

- 'and I therefore do not wish to be restricted to the a specific arrangement disclosed but intend to cover by the appended claims all changes and modifications within the spirit and scope of my invention.

lVhat I. claim as new and deslre to seeure by Letters Patentof the United States, 18

1. In a protective device, the combination with a plurality of tripping relays having members movable into trippingposition in response to. abnormal conditions, of a flexible connect-ionbctween said members whereby the movement of one member into-tripping position holds the other members inop erative.

2. In a protective device, the combination with a plurality of tripping relays having members movable into tripping position in response toabnormal conditions, of a resillent lnterlock between-said members arranged to prevent more than one of said members reaching tripping'position simultaneously. r e l 3. In-a protective device, the combination with a plurality of trippingrelayshaving members movable into tripping position in response to abnormal conditions, of an interlock between said members, and yielding means connected to said interlock to hold said members in inoperative position. 4. In a protective device, the combination with a plurality of tripping relays having members movable into tripping position in response to abnormal conditions, of a flexible interlock connected to said members and of -a' length to permit only one member at a time to reach trippingposition, and a spring arranged to exert a strain on said interlock to hold said members in position.

5. In a system of distribution, the combination with two parallel transmission lines connected to a common bus bar, of reverse current relays connected to corresponding phases of said lines, and an interlock between said relays arranged to permit only one relay at a time to reach operative position, thereby disconnecting the line controlled by said relay and simultaneously rendering the other relay inoperative.

6.1 In a system of distribution, the combination with two parallel transmission lines connected to a common bus bar, of areverse 1 current relay for each line comprising current and potential coils connected to said lines, an interlock between said relays arranged to" permit only one relay at a time to reach operative position, and means actuated when said relay reaches operative position to short circuit the current coil of the other relay.

7. In a system of distribution, the combination with a plurality of polyphase transmission lines connected to a common bus bar, of a reverse current relay for eachfline arranged to disconnect each line from the bus bars when actuated,each relay having a ourrent coil connected to corresponding phases i of said lines,"and a yielding interlock be tween said relays which permits only one of said relays to becomeoperative at any instant, whereby only that relay which corresponds to a'damaged transmission line is actuated.

8. In a system of distribution, the combi nation with two parallel transmission lines connected to a common bus bar, of reverse current relays each comprisingjeurrent and potential COllS cooperating on? a commonarmature,- the current coils of -said relays being connected to corresponding phases of said transmissionlines, and a flexible intero. lock between said armatures arranged to permit only one armature at a. time toreach operative position.

9. In. a system of distributiom fthe combi= nation with a plurality of parallel polyphase transmission lines connected to a common bus bar, of a reverse current relay for each line arranged to disconnect said line from the bus bar, each of said relays comprising a current'coil and potential'coil cooperating on'a common core, and a flexible member connected to said cores'to cause the opera tion of one relay to prevent the operation of the others, whereby only the damaged transmission line is disconnected from the bus bar.

10. In a system of distribution, the combination of parallel polyphase transmission lines connectedto a common bus bar, of a reverse current relay for each line comprising current and potential coils and a movable core common to said coils, the current coils of said relays being connected to cor- 'ergy flow and normally disconnected from said lines, and-means actuated in response to abnormal conditions of said lines to connectsaid device therewith.

13. In a system of distribution, the combi nation with parallel transmission lines connected to aicommon bus bar, and reverse current relays for said lines comprising ourrent and potential coils cooperating on a common armature, of an auxiliary relay responsive to abnormal conditions on said lines and arran to connect said coils of said relays to said transmission lines.

14. Ina system of distribution, the combination with two parallel transmission lines connected to a common bus bar, of a normally inoperative protective device for each line responsive to reverse ener flow in said line, an auxiliary relay comprising opposed currentv coils connected to corresponding phases of said transmission lines, saidrelay being arra-n to render operative any rotective device when the transmission ine controlled thereb is damaged, and means controlled bg sai protective device for rendering ine ective that relay current coil P'hich is connected to the sound transmission 15. In a system of distribution, the combination with an automatic switch arranged to be opened -by abnormal current, of a second switch in series'therewith, tripping mechanism actuated by reverse energy flow to open said second switch, and means con- Copies of this patent may be obtained for trolled by said tripping mechanism for rendering said first switch non-automatic.

16. In a system of distribution, the combiswitch, tripping mechanism responsive to abnormal conditions on said line to open said second switch, and means controlled by said tripping mechanism for rendering and first switch non-automatic.

17. A protective device comprising two tripping relays having members movable into tripping position 'in response to abnormal conditions, and a mechanical connectlon between said members which permits said members to move independently of each other when in normal position and whereby either member is mechanically held in normal position when the other member is in tripping position.

18. A protective device comprising two tripping relays having members movable into trip ing position in respdnse to, abnormal con itions, and amechanical interlock which forms a lost motion connection between said members to permit independent movement thereof when said members are Fimnnmcx Hnn'lina.

five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

